KR20150075355A - Refractive index distribution measuring method, refractive index distribution measuring apparatus, and method for manufacturing optical element - Google Patents

Refractive index distribution measuring method, refractive index distribution measuring apparatus, and method for manufacturing optical element Download PDF

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KR20150075355A
KR20150075355A KR1020140160549A KR20140160549A KR20150075355A KR 20150075355 A KR20150075355 A KR 20150075355A KR 1020140160549 A KR1020140160549 A KR 1020140160549A KR 20140160549 A KR20140160549 A KR 20140160549A KR 20150075355 A KR20150075355 A KR 20150075355A
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wavelength
phase difference
difference
refractive index
wave front
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KR1020140160549A
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Korean (ko)
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토모히로 스기모토
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캐논 가부시끼가이샤
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0228—Testing optical properties by measuring refractive power
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
    • G01M11/0271—Testing optical properties by measuring geometrical properties or aberrations by using interferometric methods
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0285—Testing optical properties by measuring material or chromatic transmission properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length

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Abstract

The refractive index distribution measuring method divides the light emitted from the light source into the reference light and the light to be detected and interferes with the reference light and the light which has passed through the object to be examined so that the light of the first and second wavelengths Measuring the phase difference between the light beams to be measured, and measuring the wavefront aberration of the light beam of each of the first and second wavelengths. The refractive index distribution measuring method includes the steps of calculating a difference in phase difference that is a difference between a phase difference in the first wavelength and a phase difference in the second wavelength and calculating a difference in phase difference between the wave front aberration in the first wavelength and the wave front aberration in the second wavelength And calculating the refractive index distribution of the inspected object on the basis of the retardation difference amount and the wave front aberration difference amount.

Figure P1020140160549

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractive index distribution measuring method, a refractive index distribution measuring method, and a manufacturing method of an optical element. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a refractive index distribution measuring method and a refractive index distribution measuring apparatus for measuring a refractive index distribution of an optical element.

The lens manufacturing method by the mold provides an advantage of the facilitated mass generation of the optical lens, but generates a refractive index distribution in the lens. The refractive index distribution generated inside the lens adversely affects the optical performance of the lens. Therefore, a method of manufacturing a lens by a mold requires a technique for measuring a refractive index distribution non-destructively in a lens manufactured by a mold.

In the measuring method disclosed in US 5,151,752, a sample to be inspected and a glass sample whose refractive index and shape are known are immersed in a first matching solution having a refractive index almost equal to the refractive index of an object to be inspected, and light can pass therethrough, . The measurement method further includes immersing the object and the glass sample in a second matching liquid having a refractive index slightly different from the refractive index of the first matching liquid, and allowing light to pass therethrough, thereby measuring the interference fringe. According to this measurement method, the shape of the object and the refractive index distribution are obtained on the basis of the measurement result using the first matching liquid and the second matching liquid. The refractive index of each of the first and second matching liquids needs to be slightly different from the refractive index of the object to be examined within a range in which the interference pattern is not too dense.

The measuring method disclosed in US 8,472,014 is a method in which an object to be examined is placed in a medium having a refractive index different from that of the object to be examined and a first transmission wave front at the first wavelength and a second transmission wave front at the second wavelength different from the first wavelength 2 transmission wave front. According to this measuring method, the measurement result of the first transmission wave front and the second transmission wave front, the first wavelength when the reference inspected having the same shape and the specific refractive index distribution as the inspected object are arranged in the medium, The refractive index distribution of the material to be inspected is calculated by removing the shape components of the material to be inspected by using each transmission wave front corresponding to the wavelength.

In the measuring method disclosed in US 5,151,752, a matching liquid having a refractive index almost equal to the refractive index of the object to be examined is required. However, a matching liquid having a high refractive index has a low transmittance. Therefore, when the interference fringes generated in the optical element of high refractive index are measured by the measuring method disclosed in US 5,151,752, only a small signal can be output from the detector, and the measurement accuracy is lowered.

In the measuring method disclosed in US 8,472,014, it is premised that the refractive index (phase refractive index) of the reference analyte is known. It is necessary that the phase index of refraction of the reference inspected object coincides with the phase refraction index of one point (for example, the center of the lens) in the inspected object. Therefore, in the refractive index distribution measuring method disclosed in US 8,472,014, there is a need for a technique for nondestructively measuring the phase refractive index at one point in the object. However, it is difficult to nondestructively measure the phase refractive index. The low coherence interference method and the wavelength scanning interference method can be used to non-destructively measure the refractive index, but the measured refractive index is not the phase refractive index but the group refractive index. Since the phase refractive index and the group refractive index do not correspond one to one with each other, the converted phase refractive index from the group refractive index includes the conversion error.

Further, the phase refractive index N p (?) Is a refractive index with respect to the phase velocity v p (?) Which is the moving velocity of the equipotential surface of light. The group refractive index N g (?) Is a refractive index with respect to the moving speed of the energy of light (the moving speed of the wave speed) v g (?).

INDUSTRIAL APPLICABILITY The present invention is directed to a refractive index distribution measuring method and a refractive index distribution measuring apparatus capable of non-destructively and highly accurately measuring the refractive index distribution of an object in another aspect.

According to an aspect of the present invention, there is provided a refractive index distribution measuring method comprising: dividing light emitted from a light source into reference light and light to be detected, and interfering with the reference light and the light which is incident on the object to be examined and transmitted through the object, A phase difference measurement step of measuring a phase difference between the reference light and the light to be measured; a wavefront aberration measurement step of measuring the wavefront aberration of the light to be measured; and a calculation step of calculating a refractive index distribution of the inspection object based on the phase difference and the wavefront aberration Wherein the phase difference measurement step includes measuring a first phase difference at a first wavelength and a second phase difference at a second wavelength different from the first wavelength, And measuring the first wave front aberration at the first wavelength and the second wave front aberration at the second wavelength, Calculating a phase difference difference amount that is a difference between the first phase difference and the second phase difference and calculating a wave front aberration difference amount that is a difference between the first wave front aberration and the second wave front aberration, And calculating a refractive index distribution of the object to be inspected based on the refractive index distribution.

According to still another aspect of the present invention, a method of manufacturing an optical element includes the steps of: molding an optical element; and measuring a refractive index distribution of the optical element using the refractive index distribution measurement method described above, And a step of evaluating the step.

According to yet another aspect of the present invention, a refractive index distribution measuring apparatus includes a light source, and a light source, which divides the light emitted from the light source into reference light and light to be detected, and transmits the reference light, the light incident on the object, A wavefront aberration measuring means for measuring a wavefront aberration of the light to be detected and a refractive index distribution of the object to be examined based on the phase difference and the wavefront aberration, Wherein the phase difference measuring means measures the first phase difference at the first wavelength and the second phase difference at the second wavelength different from the first wavelength, and the wavefront aberration measuring means Wherein the first wave front aberration at the first wavelength and the second wave front aberration at the second wavelength are measured, And the second wavefront aberration, and calculates a wavefront aberration difference amount that is a difference between the first wavefront aberration and the second wavefront aberration, and calculates a difference between the phase difference amount and the wavefront aberration difference amount The refractive index distribution of the object to be inspected is calculated.

Other features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings.

1 is a diagram showing a schematic configuration of a refractive index distribution measuring apparatus according to a first exemplary embodiment of the present invention.
Fig. 2 is a flowchart showing the calculation procedure of the refractive index distribution of the inspected object in the first exemplary embodiment.
3A and 3B are diagrams showing interference signals detected by a detector while changing the wavelength with a monochromator.
4A, 4B, and 4C are diagrams showing optical paths of rays in the coordinate system and the refractive index distribution measuring apparatus defined on the object to be inspected.
FIG. 5 is a diagram showing a schematic configuration of a refractive index distribution measuring apparatus according to a second exemplary embodiment of the present invention.
6 is a view showing a manufacturing process of a method of manufacturing an optical element according to a third exemplary embodiment of the present invention.

Various exemplary embodiments, features, and aspects of the present invention will now be described with reference to the drawings.

Fig. 1 shows a schematic configuration of a refractive index distribution measuring apparatus according to a first exemplary embodiment of the present invention. The refractive index distribution measuring apparatus according to the present exemplary embodiment is constructed based on a Mach-Zehnder interferometer. The refractive index distribution measuring apparatus includes a light source 10, an interference optical system, a container 50 capable of storing a substance 60 and a medium 70, a detector 80, a wavefront sensor 81, and a computer 90 , And the refractive index distribution of the inspected object 60 is measured. In the present exemplary embodiment, the object 60 is a refractive optical element such as a lens and a flat plate. On the other hand, the refractive index of the medium 70 need not match the refractive index of the substance 60 to be examined.

The light source 10 is a light source such as, for example, a supercontinuum light source capable of emitting light of a plurality of wavelengths. The light of a plurality of wavelengths becomes a quasi-monochromatic light after passing through the monochromator 20. The light transmitted through the monochromator 20 becomes a divergent wave after passing through the pinhole 30 and then becomes parallel light after passing through the collimator lens 40. [

The interference optical system includes beam splitters 100 and 101 and mirrors 105 and 106. The interference optical system divides the light transmitted through the collimator lens 40 into reference light that does not pass through the object 60 and object light that transmits the object 60 so that the reference light and the light to be detected interfere with each other, And guides the interference light to the detector 80. Further, the interference optical system guides the subject light to the wavefront sensor 81.

A sample 60, a medium 70, and a glass prism 110 are accommodated in a container 50. It is preferable that the optical path length of the reference light and the optical path length of the test light in the container are the same in a state in which the inspection object 60 or the glass prism 110 is not disposed in the container. Therefore, it is preferable that the side panels 50a, 50b of the container 50 have the same thickness, are parallel to each other, and have a uniform refractive index.

A part of the light to be detected which is incident on the container 50 is transmitted through the medium 70 and the substance 60 to be inspected and a part of the light to be examined is transmitted through the medium 70 and the glass prism 110. On the other hand, the reference light transmitted through the beam splitter 100 is transmitted through the side panel and the medium 70 of the container 50, and is reflected by the mirror 105. The reference light and the light to be detected are combined by the beam splitter 101 to form an interference light.

The refractive index of the medium 70 is calculated from the transmitted wavefront of a glass prism (reference subject matter) 110 which is disposed in the medium 70 and whose refractive index and shape are known. The refractive index of the medium 70 may be calculated based on the temperature of the medium 70 detected by a thermometer (not shown) and the temperature coefficient of the refractive index of the medium 70.

The mirror 105 can be driven in the direction of the preferred arrows X, Y, Z shown in Fig. 1 by a drive mechanism (not shown). The driving direction is not limited to the direction of the arrow shown in Fig. 1, but may be arbitrarily rotated (inclined) in the other direction as long as the optical path length difference between the reference light and the light to be detected can be changed by driving the mirror 105. The driving mechanism of the mirror 105 is constituted by, for example, a finely controlled piezo stage or the like. The driving amount of the mirror 105 is measured by a length measuring instrument (not shown in the drawing, such as a laser displacement meter and an encoder) and is controlled by the computer 90. The optical path length difference between the reference light and the light to be detected can be adjusted by controlling the position of the mirror 105 while the drive mechanism is connected to the computer 90. [

The interference light formed in the beam splitter 101 is detected by a detector 80 (for example, a CCD (Charge-Coupled Device) sensor or a CMOS (Complementary Metal-Oxide Semiconductor) sensor) through an imaging lens 45 do. The interference signal detected by the detector 80 is transmitted to the computer 90. The detector 80 is disposed at a position conjugate with respect to the position of the inspected object 60 and the glass prism 110 and the imaging lens 45.

Since the refractive indexes of the analyte 60 and the medium 70 are different from each other in the present exemplary embodiment, most of the interference fringes formed of the light to be detected and the reference light passing through the analyte 60 are too dense to resolve the interference fringes do. Therefore, the detector 80 can not measure most of the interference fringes formed by the reference light and the light that is transmitted through the inspected object 60. However, in the present exemplary embodiment, the detector 80 does not need to detect all of the interference signals acquired from the light transmitted through the inspected object 60. The detector 80 may detect the interference signal acquired from the light transmitted through the medium 70 or the glass prism 110 and the interference signal acquired from the light transmitted through the center of the object 60. [

A part of the light that has passed through the inspected object 60 is reflected by the beam splitter 101 and is detected by the wavefront sensor 81 (for example, a Shack-Hartmann wavefront sensor). The signal detected by the wavefront sensor 81 is transmitted to the computer 90 and is calculated as the transmission wavefront of the subject light transmitted through the inspected object 60. [

The computer 90 includes a calculation unit configured to calculate a refractive index distribution of the inspected object 60 on the basis of the detection result of the detector 80 and the detection result of the wavefront sensor 81, And a control unit configured to control the wavelength of the light and the driving amount of the mirror 105, and is constituted by a central processing unit (CPU) or the like.

The interference optical system is adjusted such that the optical path lengths of the reference light and the light to be detected are equal to each other in a state in which the inspected object 60 is not disposed in the container 50. A method of adjusting the interference optical system will be described below.

Referring to FIG. 1, the refractive index distribution measuring apparatus acquires an interference signal obtained by interfering the reference light and the light under test in a state in which the analyte 60 is not disposed on the optical path of the light. At this time, the phase difference? 0 (?) Between the reference light and the light to be detected and the interference intensity I? 0 (?) Between the reference light and the light to be detected are expressed by the following formula (1).

Figure pat00001
(One)

However, λ denotes the wavelength in air of the light emitted from the light source (10), Δ 0 denotes the optical path length difference between the reference beam and the test light, I 0 represents the sum of the reference light intensity and the test light intensity,

Figure pat00002
Represents the degree of visibility. Equation (1), when the difference Δ 0 is not zero, the interference intensity I φ0 (λ), we propose that the vibration function. Therefore, in order to make the optical path lengths of the reference light and the light to be equal to each other, the mirror 105 may be driven so that the interference signal does not have a vibration function. At this time, the difference? 0 becomes zero.

2 is a flowchart showing a calculation procedure for calculating the refractive index distribution of the material 60 to be inspected. In step S10, the user places the inspected object 60 on the optical path of the light to be examined. Next, in step S20 (the phase difference measurement step), the computer 90 is in the phase difference is the first phase difference φ (λ 1) and a second wavelength λ 2 between the reference beam and the test light at the λ 1, the first wavelength The second phase difference? (? 2 ), which is the phase difference between the reference light and the light to be detected, is calculated. It is preferable that the first wavelength? 1 and the second wavelength? 2 are different from each other, for example, 450 nm and 650 nm. The phase difference? (?) And the interference intensity I (?) At the wavelength? Are expressed by Equation (2). In the present exemplary embodiment, the phase difference? (?) Passes through the lens 70 and the side panel 50a and 50b of the container 50 and the light passing through the center of the lens (the inspected object 60) Represents the phase difference between the reference light and the reference light.

Figure pat00003

Figure pat00004
(2)

However, n samle (λ, 0,0) denotes a refractive index in the center of the analyte (60), medium n (λ) denotes a refractive index of the medium (70), L (0,0) is the analyte (60 ). ≪ / RTI > The phase difference? (?) Measured in this step includes an unknown number 2? M (?) (M (?) Corresponding to an integer multiple of 2?

3A shows an interference signal of a spectral range that can be measured by the detector 80 shown in Fig. The interference signal is a vibration function because the phase difference? (?) Depends on the wavelength?. In Fig. 3A,? 0 represents the wavelength when the phase difference? (?) Takes the extreme value. Since the oscillation period of the interference signal becomes longer in the vicinity of the wavelength? 0 , the interference signal can be measured easily. The wavelength? 0 can be adjusted by driving the mirror 105 to change the value of the difference? 0 .

The phase difference? (?) Can be measured by using the phase shift method. A method of measuring the phase difference? (?) Using the phase shift method is shown below. First, the computer 90 acquires an interference signal while driving the mirror 105 by a small amount. The intensity I k (?) Of the interference light acquired when the phase shift amount (= drive amount x 2? /?) Of the mirror 105 is? K (k = 0, 1, ..., M- 3).

Figure pat00005
(3)

When the coefficients a 0 , a 1 and a 2 are calculated by the least square method, the phase difference? (?) Is expressed by equation (4) using the phase shift amount? K and the interference intensity I k (?). The calculated phase difference? (?) Is convoluted with 2 ?. Therefore, it is necessary to perform an operation (phase unwrapping) of connecting phases in a phase jump of 2 [pi].

Figure pat00006
(4)

In the above calculation, the first phase difference? (? 1 ) at the first wavelength? 1 and the second phase difference? (? 2 ) at the second wavelength? 2 are calculated as in the equation (5).

Figure pat00007
(5)

In Figure 2 returns to a step S30, the computer 90 includes a first phase difference φ (λ 1) and the difference between the second phase difference φ (λ 2) phase difference amount φ (λ 2) -φ (λ 1) . The phase difference difference? (? 2 ) -? (? 1 ) is expressed by Equation (6).

Figure pat00008
(6)

Integer m (λ 1) and an integer m (λ 2) it is unknown, but constant m (λ 1) and the integer m difference between the integer m (λ 2) between (λ 2) - m (λ 1) is, in Figure 3a Can be calculated from the indicated interference signal. When the first wavelength? 1 and the second wavelength? 2 are the wavelengths shown in FIG. 3A, there is a difference between the first wavelength? 1 and the wavelength? 0 at which the phase difference? (? There is a difference of two cycles between the two wavelengths? 2 and? 0 . That is, the equations | m (? 1 ) - m (? 0 ) | = 1 and | m (? 2 ) - m (? 0 ) | = 2. Whether the extreme value? (? 0 ) is the maximum value or the minimum value can be calculated from the measurement conditions such as the design value of the substance to be examined 60 and the refractive index of the medium 70. If the extreme value φ (λ 0) is the maximum value, the integer m (λ 1) of the difference - m (λ 0) = -1 , and m (λ 2) - since the m (λ 0) = -2, the difference The integer can be calculated as m (? 2 ) -m (? 1 ) = -1.

Phase difference amount φ (λ 2) -φ (λ 1) of Equation (6), the refractive index n sample (λ 1, 0,0) in the first wavelength λ 1 of the analyte 60 and the second wavelength a physical quantity related to the refractive index n sample (λ 2, 0,0) of the λ 2. The physical quantity f (λ 1 , λ 2 ) expressed by the following equation (7) is used in order to make the relationship between the refractive index n sample (λ 1 , 0,0) and the refractive index n sample (λ 2 , (6).

Figure pat00009
(7)

To continue, step S40 (the wave front aberration measurement step), the computer 90 comprises a wave-front aberration W (λ 1, x, y) of the first wavelength analyte 60 in the λ 1 and the second wavelength λ 2 The wave front aberration W (? 2 , x, y) of the inspected object 60 in the optical axis direction is measured through the wavefront sensor 81. In the present exemplary embodiment, the method of measuring the wavefront aberration is performed in accordance with Step A shown in Fig.

First, in step S401, the computer 90 is transmitted wavefront W m (λ 1, x, y) and the analyte of interest in the second wavelength λ 2 (60 of the analyte 60 in the λ 1, the first wavelength (? 2 , x, y) of the transmitted wavefront W m (? It is unnecessary to make the wavefront sensor 81 shield the unnecessary light from entering the wavefront sensor 81 (not shown in the drawing) to measure the transmission wavefront of the inspected object 60, An aperture or a shutter is disposed. The transmission wave front W m (λ, x, y) of the inspected object 60 at the wavelength λ passing through the point (x, y) in the inspected object 60 shown in FIG. 4A is expressed by the following equation (8).

Figure pat00010
(8)

However, L a (x, y), L b (x, y), L c (x, y), and L d (x, y) are geometric distances between components arranged along the light ray shown in FIG. . The ray shown in Fig. 4B is a ray passing through a point (x, y) inside the analyte 60 shown in Fig. 4A. L (x, y) represents the geometric distance of the optical path of the light in the inspected object 60, that is, the thickness of the inspected object 60 in the direction of the light ray. n sample (?, x, y) is the refractive index at the wavelength? of the analyte 60. In the equation (8), for the sake of simplicity, the thickness of each of the side panels 50a, 50b of the container 50 is ignored.

In step S402, the computer 90 is a specific refractive index having a distribution criteria analyte the transmission in the first wavelength λ 1 wavefront W sim (λ 1, x, y) and the transmission wave-front in the second wavelength λ 2 It calculates the W sim (λ 2, x, y). This step is to calculate the transmission wavefront when it is assumed that the reference inspected object having the same shape as the inspected object 60 and having the same refractive index distribution is disposed at the position of the inspected object 60 in step S401 .

It is necessary to input the phase index of refraction of the reference analyte when calculating the transmission wavefront of the reference analyte. It is ideal that the phase index of refraction of the reference subject coincides with the phase refraction index of a point inside the subject 60. For example, when the phase index of refraction of the reference inspected object coincides with the phase refractive index n sample (λ, 0, 0) of the center of the inspected object 60, the transmitted wavefront W sim , x, y) is expressed by the following equation (9). Further, by calculating the difference between the equations (8) and (9), the refractive index distribution GI (?, X, y) is calculated.

Figure pat00011
(9)

Figure pat00012
(10)

It is assumed that the phase refractive index of the reference analyte does not coincide with the phase refractive index n sample (λ, 0, 0) of the center of the inspected object 60. (Λ, x, y) of the inspected object 60 is calculated as shown in Expression (11) when the phase index of refraction of the reference inspected object is n sample (λ, 0,0) + Δn do.

Figure pat00013
(11)

Since the second term on the right side of Expression (11) is a function of the position (x, y), the refractive index distribution GI '(λ, x, y) is different from the actual refractive index distribution GI I know. Therefore, in order to accurately calculate the refractive index distribution of the inspected object 60, the phase refractive index of any one point (the center of the inspected object 60 in this exemplary embodiment) inside the inspected object 60 is measured with high precision must do it. However, it is difficult to nondestructively measure the phase refractive index of the analyte 60. In order to solve this problem, in the present exemplary embodiment, the following alternative method is used to reduce the refractive index distribution error derived from "? N (?) &Quot;.

More specifically, the phase refractive index n sample (?, 0,0) +? N (?) Of the reference analyte is determined in such a manner as to satisfy the relationship represented by the following equation (12). In the formula 12, the first wavelength of the refractive index of the phase reference analyte in the sample n 1 λ (λ 1, 0,0) + δn (λ 1) and that, based on the test of the second wavelength λ 2 The phase refractive index of water is called n sample (λ 2 , 0,0) + Δn (λ 2 ).

Figure pat00014

Figure pat00015
(12)

Using the phase index of refraction of the reference analyte determined by equation (12), the transmitted wavefront W sim (λ, x, y) of the reference analyte is expressed as:

Figure pat00016
(13)

In step S403, the computer 90 calculates the wave front aberration W (λ, x, y) corresponding to the difference between the transmission wave front W m (λ, x, y) of the inspected object and the transmission wave front W sim , y) are calculated as shown in equation (14).

Figure pat00017
(14)

In step S40 according to the above-described step A, the computer 90 is in the first wave-front aberration W (λ 1, x, y) and the second wavelength λ 2 of the analyte 60 in the λ 1, the first wavelength The second wave front aberration W (? 2 , x, y) of the inspected object 60 is measured. The first wave front aberration W (? 1 , x, y) and the second wave front aberration W (? 2 , x, y) are expressed by the following mathematical expression (15).

Figure pat00018
(15)

Then, in step S50, the computer 90 calculates the wavefront aberration difference amount W (? 2 , x, y) -W (? 1 , x, y) as shown in the following equation (16). Furthermore, when the approximate expression (17) is used, the expression (16) is transformed into the following expression (18).

Figure pat00019
(16)

Figure pat00020
(17)

Figure pat00021
(18)

The second term on the right side of the equation (18) is a refractive index distribution calculation error derived from "? N (?) &Quot;, which corresponds to the second term of the equation (11). However, in the present exemplary embodiment, the second term on the right side of the equation (18) becomes zero because the phase refractive index of the reference analyte is determined so as to satisfy the relationship represented by the equation (12). More specifically, in step S60, the computer 90 is phase difference amount φ (λ 2) -φ (λ 1) using the equation (7), a formula (12), a wave front aberration difference amount W (λ 2, x, y) - calculates W (on the basis of the equation (16) for calculating λ 1, x, y), the refractive index distribution of GI (λ 1, x, y ) as shown in equation (19) below. If further use of further, Formula (17), the computer 90 is the refractive index distribution of the second wavelength λ 2 on the basis of the refractive index distribution of GI (λ 1, x, y) in the first wavelength λ 1 GI (? 2 , x, y). On the other hand, "? N (?)" Still remains in the following expression (19), but the influence of "? N (?)" Remaining in the form of these expressions on the refractive index distribution is negligibly small.

Figure pat00022
(19)

As described above, the high-precision measurement possible phase difference amount φ (λ 2) -φ (λ 1) and the wave front aberration difference amount W (λ 2, x, y ) - 2 one physical value of W (λ 1, x, y) It is possible to measure the refractive index distribution of the inspected object 60 with high precision in a nondestructive manner.

In the present exemplary embodiment, the refractive index distribution in a computer (90) after calculating the refractive index distribution of GI (λ 1, x, y) of the λ 1, the first wavelength, the second wavelength λ 2 GI (λ 2 , x, y). Instead, the computer 90 calculates the refractive index distribution GI (? 2 , x, y) at the second wavelength? 2 on the basis of the equations (16) and (17) 1 , the refractive index distribution GI (? 1 , x, y) in the refractive index distribution G1 may be calculated.

In this exemplary embodiment, the computer 90 is the formula (6) as shown phase difference amount φ (λ 2) -φ (λ 1) to Formula (7) as indicated physical quantity f (λ 1, λ 2) in accordance with And determines the phase refractive index of the reference inspected object based on the physical quantity f (? 1 ,? 2 ). Thereby, the computer 90 reduces the refractive index distribution error caused by the error? N (?) Of the phase refractive index.

The physical quantity used for determining the phase index of refraction of the reference object is not limited to "f (λ 1 , λ 2 )", but may be a physical quantity calculated from the phase difference difference φ (λ 2 ) -φ (λ 1 ). For example, "g (λ 1 , λ 2 )" or "h (λ 1 , λ 2 )" in the following equation (20) can be replaced by physical quantities. Alternatively, without calculating a physical quantity such as "f (λ 1 , λ 2 )", the computer 90 may directly use the physical quantity in the form of the phase difference difference φ (λ 2 ) -φ (λ 1 ).

Figure pat00023
(20)

In the present exemplary embodiment, the computer 90 calculates the refractive index distribution GI (? 1 , x, y) without knowing the value of the refractive index n sample (? 1 , 0, 0) of the center of the inspected object 60 . Furthermore, the computer 90 can calculate the refractive index n sample (λ 1 , 0, 0) of the center of the actual inspected object 60 by performing the following calculation.

Θ indicated by equation (21) below, the refractive index distribution that is calculated in accordance with equation (11) GI '(λ, x, y) and a refractive index distribution that is calculated in accordance with equation (19) GI (λ 1, x, y). < / RTI > Calculating the phase index n sample (λ, 0,0) + Δn (λ) of the reference analyte that is likely to decrease the value Θ causes the computer 90 to determine the index of refraction n sample (λ 1 , 0,0) can also be calculated.

Figure pat00024
(21)

In general, it is difficult to nondestructively measure the phase refractive index of an object to be examined. However, if the refractive index distribution of the object to be examined is known, the phase refractive index of the object can be measured non-destructively by using the method represented by the equation (21). In the present exemplary embodiment, the computer 90 has calculated the refractive index n sample (λ 1 , 0, 0) of the center of the inspected object 60 at the first wavelength λ 1 , The refractive index n sample (? 2 , 0, 0) of the center of the object 60 at the wavelength? 2 can also be calculated by the above method.

Generally, a lens manufactured by a lens or a mold produced by grinding or polishing, in which dispersion distribution of the refractive index hardly occurs, establishes the approximate expression (17). On the other hand, a lens in which a dispersion distribution of a refractive index is intentionally generated to reduce chromatic aberration does not satisfy the approximation formula (17). The measurement of the refractive index distribution of the dispersed distribution lens using the present exemplary embodiment involves an error, so care must be taken.

In the present exemplary embodiment, it is assumed that the inspected object 60 and the reference inspected object have the same shape L (x, y). If the shape of the inspected object 60 differs from the shape of the reference inspected object, the calculated refractive index distribution includes an error. Therefore, it is preferable to measure the shape of the subject 60 in advance using a pin measurement method or the like, and to apply the measured shape to the shape of the reference subject. Alternatively, it is possible to apply the design value L (x, y) as the shape of the reference inspected object and remove the shape error (shape component) delta L (x, y) from the design value of the inspected object 60. [ The shape error δL (x, y) of the object 60 (x, y) of each of the two kinds of media having different refractive indices (for example, oil having a refractive index of 1.70 as a first medium and oil having a refractive index of 1.75 as a second medium) ), And can be removed by performing the flow shown in Fig.

(K, k) which is the difference between the first phase difference and the second phase difference of the inspected object 60 in the kth medium when the shape of the object 60 is L (x, y) +? L The phase difference amount? K (? 2 ) -φ k (? 1 ) of the phase difference is expressed by the following equation (22). However, k = 1, 2.

Figure pat00025
(22)

n k medium (?) represents the refractive index of the kth medium ,? 0k represents the optical path length difference between the reference light and the light under test in the state where the inspected object 60 is not disposed in the kth medium, and m k (?) represents an integer in the kth medium. From the first medium, a first phase difference amount φ 1 (λ 2) -φ 1 (λ 1) and a second phase difference amount φ 2 (λ 2) -φ 2 (λ 1) of the second medium in the , And the shape component L (0, 0) + delta L (0, 0) are removed, the physical quantity f (lambda 1 , lambda 2 ) can be obtained as in the following equation (23).

Figure pat00026
(23)

The k-th wave front aberration which is the difference between the first wave front aberration W k (λ 1 , x, y) of the inspected object 60 in the kth medium and the second wave front aberration W k (λ 2 , x, y) Consider the difference W k (λ 2 , x, y) -W k (λ 1 , x, y). The analyte-like L (x, y) + δL (x, y) one time, the wave front aberration difference amount of k W k (λ 2, x , y) - W k (λ 1, x, y) is, (25) using the equations (12), (23), and the following approximate equation (24).

Figure pat00027
(24)

Figure pat00028
(25)

A first wave-front aberration difference amount W 1 (λ 2, x, y) in the first medium - W 1 (λ 1, x , y) and the second wavefront aberration difference amount of the second medium W 2 (λ 2, x, y) - W 2 ( λ can be from 1, x, y), the shape component δL (x, y) and remove δL (0,0). Using the equation (17), the refractive index distribution GI (? 1 , x, y) is calculated as in the following equation (26).

Figure pat00029
(26)

The refractive index of the medium changes with the change of the temperature of the medium. Therefore, even if one kind of medium is used, the refractive index distribution according to the present exemplary embodiment under two kinds of temperature values is the same as that of the refractive index distribution according to the present exemplary embodiment in two kinds of mediums having different refractive indexes . That is, the refractive indexes of the first medium and the second medium in the present exemplary embodiment may be different from each other. Two kinds of media may be used, or one kind of media having different temperature values may be used. Therefore, the shape components of the inspected object 60 may be removed using two kinds of temperature values.

The influence of the shape error δL (0, 0) of the center of the inspected object 60 on the phase difference difference φ (λ 2 ) -φ (λ 1 ) is removed by using two kinds of media or two kinds of temperature values , It can be reduced by using the following method.

The method includes disposing the object 60 in the medium 70 having a group refractive index equal to the group refractive index of the object 60 at a specific wavelength, setting the difference in optical path length as? 0 = 0, And acquiring the interference signal as shown in Fig. The interference signal indicates the wavelength dependency of the phase difference between the reference light and the light to be detected. The wavelength? 0 shown in FIG. 3B corresponds to a specific wavelength at which the group refractive index of the analyte 60 and the group refractive index of the medium 70 are equal to each other.

As shown in Figure 3b, if the phase difference φ (λ) is from a wavelength λ 0 to take extreme value, selecting a first wavelength λ 1 'and a second wavelength λ 2' in the distance of the same cycle, φ (λ 1 ') =? (? 2 ') is obtained. At this time, the third term on the right side of the following equation (27) becomes zero and the physical quantity f (? 1 ',? 2 ') becomes a value which does not depend on the shape component of the inspected object 60.

More specifically, the "phase difference φ (λ 2 in the second wavelength λ 2) the phase difference φ (λ 1), in the first wavelength λ 1 so that the equal to each other a first wavelength λ 1 and the second wavelength λ 2 Can be selected. Thus, the effect of the shape error δL (0, 0) of the center of the inspected object 60 on the phase difference amount φ (λ 2 ) -φ (λ 1 ) can be reduced.

Figure pat00030
(27)

In this exemplary embodiment, various wavelengths are generated and scanned by a combination of a light source emitting a plurality of wavelengths of light and a monochromator. A supercontinuum light source is used as a light source for emitting light of a plurality of wavelengths, but a superluminescent diode (SLD), a short pulse laser source, a halogen lamp, and the like can be substituted. Instead of a combination of a light source and a monochromator that emit light of a plurality of wavelengths, a wave swept light source or a multi-line laser that discretely emits light of a plurality of wavelengths may be used. The light source that emits light of a plurality of wavelengths is not limited to a single light source, and may be a combination of a plurality of light sources. In the present exemplary embodiment, it is sufficient to use a light source that emits light of two or more kinds of wavelengths, and the wavelengths thereof are different from each other to the extent that the difference between the wavelengths is measurable.

In this exemplary embodiment, the computer 90 measures the phase difference of the center of the inspected object 60 (the coordinates (0, 0) shown in Fig. 4A). This is because the light passing through the center of the object 60 to be inspected is straight without being deflected, and therefore, it is easy to measure. Of course, the computer 90 may measure the phase difference of arbitrary coordinates (x, y) instead of the center of the inspected object.

In the present exemplary embodiment, a Shack-Hartmann wavefront sensor is used as the wavefront sensor 81. The wavefront sensor 81 may be a wavefront sensor capable of measuring a transmission wavefront having a large aberration. As the wavefront sensor 81, a wavefront sensor using a Hartmann operation or a wavefront sensor using a shearing interferometer such as a Talbot interferometer can be used.

In the present exemplary embodiment, a Mach-Zehnder interferometer is used in the interference optical system. Instead, an interferometer capable of measuring the optical path length difference between the reference light and the light to be detected, such as a Twyman-Green interferometer, can be used instead. Further, in the present exemplary embodiment, the phase difference and the wavefront aberration are calculated as a function of wavelength, but may be calculated as a function of frequency.

In the present exemplary embodiment, the integer m (? 2 ) -m (? 1 ) is calculated from the interference signal shown in FIG. 3A in the equation (6). Since the integer m (? 2 ) -m (? 1 ) is a discrete value, it can be calculated using measurement conditions such as the design value of the analyte 60 and the refractive index of the medium 70. That is, the integer m (lambda 2 ) -m (lambda 1 ) can be calculated by reproducing the measuring apparatus shown in Fig. 1 on a calculator and using the design value for the calculation instead of calculating from the interference signal.

In the present exemplary embodiment, the refractive index distribution of the inspected object 60 is measured with a configuration in which the light to be examined is vertically incident on the material 60 to be inspected. However, the refractive index distribution of the material 60 to be inspected can be measured even in the configuration in which the light to be examined is obliquely incident on the material 60 to be inspected. It is possible to calculate the refractive index distribution of the inspected object 60 in the direction of the optical axis by measuring the refractive index distribution of the inspected object 60 by the oblique entry configuration.

The optical path length distribution (= refractive index distribution 占 L (x, y)) functions as a physical quantity representing the optical performance of the mold lens, and can be substituted by a refractive index distribution. Therefore, the refractive index distribution measuring method (refractive index distribution measuring apparatus) according to the present exemplary embodiment can also be called optical path length distribution measuring method (optical path length distribution measuring apparatus).

In the exemplary embodiment of the present invention, a method of calculating the refractive index distribution of the inspected object 60 without using the reference inspected object used in the first exemplary embodiment will be described. 5 is a diagram showing a schematic configuration of a refractive index distribution measuring apparatus according to a second exemplary embodiment. In Fig. 5, the same components as those in the first exemplary embodiment are denoted by the same reference numerals. In the second exemplary embodiment, the transmitted light passing through the inspected object 60 is made substantially parallel by inserting the object 60 between the two kinds of lenses. Since the transmitted light is almost parallel light, a wavefront sensor capable of measuring a wavefront of a large aberration such as a Shack-Hartmann wavefront sensor is not necessary, and the transmitted light can be measured only by the detector 80 that measures the interference pattern between the reference light and the light to be detected .

The light source 11 in the present exemplary embodiment is a multi-line gas laser (for example, argon laser or krypton laser) which emits light at a plurality of wavelengths discretely. In this exemplary embodiment, the phase difference? (?) Between the reference light and the light to be measured and the wave front aberration W (?, X, y) are measured using a Mach-Zhenter interferometer.

In this exemplary embodiment, in order to remove the influence of the refractive power of the inspected object 60, a medium (not shown) between the first reference lens 120 and the second reference lens 125 having the same refractive index as the inspected object 60 (60) is inserted through the opening (71). The inspected object 60, the first reference lens 120, the second reference lens 125, and the medium 71 constitute the test unit 200. The first reference lens 120 has a surface having substantially the same shape as the shape of the first surface of the inspected object 60 and the second reference lens 125 has the shape of the second surface of the inspected object 60 As shown in Fig. The surface shapes of the object 60, the first reference lens 120, and the second reference lens 125 and the refractive indexes of the first reference lens 120 and the second reference lens 125 are known amounts.

The first reference lens 120 and the second reference lens 125 have a refractive index distribution of almost zero and are manufactured by grinding or polishing. The refractive index and the surface shape of the inspected object 60, the first reference lens 120, and the second reference lens 125 are set so that the interference pattern measured by the measuring apparatus according to the present exemplary embodiment is not so dense The degree to which the pattern can be solved). Between the first reference lens 120 and the inspected object 60 and between the inspected object 60 and the second reference lens 125, a medium 71 (e.g., oil ) Is applied.

The light emitted from the light source 11 is split by the monochromator 20 into quasi-monochromatic light. Subsequently, the quasi-monochromatic light enters the pinhole 30. The wavelength of the quasi-monochromatic light is controlled by the computer 90. The light transmitted through the pinhole 30 becomes divergent light and becomes collimated light by the collimator lens 40. The parallel light is divided into transmitted light (reference light) and reflected light (light to be detected) by the beam splitter 100.

The light that is reflected by the beam splitter 100 is reflected by the mirror 106 and passes through the inspection unit 200 (the first reference lens 120, the medium 71, the inspection object 60, the medium 71 ), And the second reference lens 125), and enters the beam splitter 101. [ On the other hand, the reference light transmitted through the beam splitter 100 is transmitted through the compensation plate 130, reflected by the mirror 105, and incident on the beam splitter 101. The compensation plate 130 is a glass block made of the same material as the first reference lens 120 and the second reference lens 125.

The reference light and the reference light are combined by the beam splitter 101 to form an interference light. The formed interference light is detected by the detector 80 through the imaging lens 45. [ The interference signal detected by the detector 80 is sent to the computer 90. The detector 80 is arranged at a position of the inspected object 60 and a position conjugate with respect to the imaging lens 45. [

A method of calculating the refractive index distribution of the inspected object 60 in the present exemplary embodiment will be described below. In the present exemplary embodiment, first, the inspected object 60 is inserted between the first reference lens 120 and the second reference lens 125 through the medium 71 to constitute the test unit 200, The unit 200 is placed on the optical path of the light to be examined. The computer 90 calculates the first phase difference? (? 1 ) at the first wavelength, the first wave front aberration (? 1 ) at the first wavelength, and the second phase difference? a W (λ 1, x, y ), the second phase difference φ (λ 2), and a second wave aberration W (λ 2, x, y ) in the second wavelength is measured. In the present exemplary embodiment, the wave front aberration W (?, X, y) and the phase difference? (?) Can be measured simultaneously. Further, in the present exemplary embodiment, the computer 90 measures the phase difference in the coordinates (a, b) thereof, not the phase difference of the center of the inspected object 60. [ The phase difference? (?) At the wavelength? And the wave front aberration W (?, X, y) are expressed by the following equation (28).

Figure pat00031
(28)

Configuration of L A (x, y), L B (x, y), L C (x, y), and L D (x, y) is an insertable unit 200 disposed along the rays shown in Figure 4c Represents the geometric distance between elements. FIG. 4C is drawn by ignoring the deflection of light rays caused by refraction on each surface. L (x, y) is the thickness of the analyte of interest (60), L A (x, y) is the first reference lens thickness, the (120) L D (x, y) is the thickness of the second reference lens 125 .

It is assumed that the thicknesses L A (x, y), L (x, y), and L D (x, y) are measured by a separate surface shape measuring method and are defined here as known amounts. The distance L B (x, y) and the distance L C (x, y) between the first surface of the inspected object 60 and the second surface of the first reference lens 120, Plane and the first surface of the second reference lens 125 are slightly different from each other. The distances L B (x, y) and L C (x, y) are also known since the thickness L A (x, y), L (x, y), and L D . L +? L is the thickness of the compensation plate 130, which is known. In the present exemplary embodiment, the distance L A (x, y), L B (x, y), L (x, y), L C (x, y), as shown by the following equation (29), And L D (x, y) is equal to the thickness of the test unit 200. [ The thickness of the test unit 200 is known.

Figure pat00032
(29)

n 0 (?) is the phase refractive index of the first reference lens 120, the second reference lens 125, and the compensation plate 130, and is known. In the present exemplary embodiment, it is assumed that the first reference lens 120, the second reference lens 125, and the compensation plate 130 have the same phase refractive index, and that the refractive index distribution is uniform. n medium (?) represents the phase refractive index of the medium 71. The computer 90 measures the temperature of the medium 71 using a thermometer (not shown), and calculates the phase index n medium (?) Of the medium 71 based on the measured temperature. ? 0 is a distance between the reference light and the reference light when the first reference lens 120, the inspected object 60, the second reference lens 125, and the compensation plate 130 are not disposed on the reference light path or the light path Represents the difference in optical path length between the light beams to be detected.

If the integer m (?) In Expression (28) is specified, the phase refractive index n sample (?, A, b) is calculated from the phase difference? (?). The refractive index distribution GI (λ, x, y) is expressed by the following equation (30) based on the phase refractive index n sample (λ, a, b), the wave front aberration W (λ, x, y) ).

Figure pat00033
(30)

However, since the phase index of refraction of the object 60 greatly changes during manufacture by molding, it is difficult to specify the integer m (). In other words, it is difficult to non-destructively measure the phase refractive index of the analyte 60. If the integer m () is erroneously designated as? M, the refractive index distribution GI (?, X, y) obtained from the equation (30) includes the error of? M / L (x, y).

In the present exemplary embodiment, instead of specifying the integer m (?) As in the first exemplary embodiment, the computer 90 may calculate the integer m (? 1 ) at the first wavelength? 1 and the integer m And the difference m (? 2 ) -m (? 1 ) from the integer m (? 2 ) at the wavelength? 2 . Since it is easy to specify the difference m (? 2 ) -m (? 1 ), it is possible to prevent the error of? M / L (x, y) from being mixed in the refractive index distribution GI (?, X, y).

The computer 90 calculates the phase difference difference φ (λ 2 ) -φ (λ 1 ) and the wavefront aberration difference amount W (λ 2 , x, y) -W (λ 1 , y). Further, the computer 90 calculates the physical quantity F (λ 1, λ 2) from the following equation (32) the retardation difference amount φ (λ 2) -φ (λ 1) , as indicated by.

Figure pat00034
(31)

Figure pat00035
(32)

Then, the computer 90 calculates the phase refractive index n sample (λ 1 , a, b) + Δn (λ 1 ) of the inspected object 60 at the first wavelength λ 1 as if it satisfies the following equation (33) and a second wavelength to determine the phase sample refractive index n (λ 2, a, b) + δn (λ 2) of the analyte 60 in the λ 2.

Figure pat00036
(33)

Finally, the computer 90 uses the equation (17), equation (31), equation (32) and equation (33) to calculate the index of refraction GI (? 1 , x, y).

Figure pat00037
(34)

In the present exemplary embodiment, it is assumed that the shape L (x, y) of the inspected object 60 is known. Between the first reference lens 120 and the inspected object 60 and between the inspected object 6 and the second reference lens 125 even when the shape L (x, y) of the inspected object 60 is not known The third term on the right side of the equation (34) is regarded as zero if the distances L B (x, y) and L C (x, y) which are the gaps of the test object 60 are negligibly small with respect to the thickness of the material 60 can do. That is, the following approximate expression (35) is established. Therefore, the influence of the shape error of the inspected object 60 can be ignored. The calculation formula of the refractive index distribution GI (? 1 , x, y) when the shape L (x, y) of the inspected object 60 is not known is expressed by the following equation (36).

Figure pat00038
(35)

Figure pat00039
(36)

Alternatively, if two kinds of media are used as in the first exemplary embodiment, the shape error? L (x, y) can be removed. In the present exemplary embodiment, the object 60 is not immersed in two kinds of mediums as in the first exemplary embodiment, but the object 60 is not immersed between the first reference lens 120 and the object 60, Only two types of medium are prepared as the medium 71 to be applied between the first reference lens 125 and the second reference lens 125. When the above-described measurement is performed on the two types of media, the shape components can be removed in the same manner as in the first exemplary embodiment.

It is also possible to feed back the measurement result of the refractive index distribution obtained by the measuring apparatus or the measurement method described in the first exemplary embodiment or the second exemplary embodiment and the measurement result of the refractive index to the manufacturing method of the optical element such as a lens .

Fig. 6 shows an example of a manufacturing process of an optical element by molding.

The optical element is manufactured by a designing step (S600) of an optical element, a designing step (S602) of a mold, and a molding step (S604) of an optical element using the mold. Thereafter, the shape accuracy of the molded optical element is evaluated (S606). If the shape accuracy is insufficient (NG in S606), the mold is corrected (S607) and molding is performed again. If the shape accuracy is good (OK in S606), the optical performance of the optical element is evaluated (S608). By integrating the refractive index distribution measuring method or the refractive index distribution measuring method according to the above-described exemplary embodiment in the optical performance evaluation step (OK in S608), the optical element can be accurately mass produced by molding (S610).

If it is evaluated that the optical performance is low (NG in S608), the optical element corrected for the optical surface is redesigned (S609).

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims (16)

A phase difference measurement step of dividing the light emitted from the light source into the reference light and the light to be detected and measuring the phase difference between the reference light and the light to be examined by interfering with the light to be examined which has passed through the object to be examined, Wow,
A wavefront aberration measuring step of measuring the wavefront aberration of the light to be detected,
And a calculating step of calculating a refractive index distribution of the inspected object based on the phase difference and the wavefront aberration, the refractive index distribution measuring method comprising:
The phase difference measuring step may include measuring a first phase difference at a first wavelength and a second phase difference at a second wavelength different from the first wavelength,
The wavefront aberration measuring step may include measuring a first wave front aberration at the first wavelength and a second wave front aberration at the second wavelength,
Wherein said calculating step calculates a phase difference difference amount that is a difference between said first phase difference and said second phase difference and calculates a wave front aberration difference amount which is a difference between said first wave front aberration and said second wave front aberration, And calculating the refractive index distribution of the inspected object on the basis of the wavefront aberration difference amount.
The method according to claim 1,
Wherein the wavefront aberration measuring step calculates the first wavefront aberration as a difference between the transmission wavefront of the inspected object at the first wavelength and the transmission wavefront at the first wavelength of the reference inspected object having the specific refractive index profile, Further comprising calculating a second wavefront aberration as a difference between a transmission wavefront of the inspected object at the second wavelength and a transmission wavefront at the second wavelength of the reference inspected object.
3. The method according to claim 1 or 2,
Wherein the phase difference measuring step measures the first phase difference at the first wavelength and the second phase difference at the second wavelength by disposing the analyte in a first medium having a first refractive index, Further comprising arranging the object to be examined in a second medium having a second refractive index different from that of the first medium, and measuring a first phase difference in the first wavelength and a second phase difference in the second wavelength,
Wherein the wavefront aberration measuring step measures the first wavefront aberration at the first wavelength and the second wavefront aberration at the second wavelength by disposing the object to be examined in the first medium, Further comprising arranging the object to be examined to measure a first wave front aberration at the first wavelength and a second wave front aberration at the second wavelength,
The calculating step may include calculating a first phase difference amount that is a difference between the first phase difference and the second phase difference measured by disposing the subject in the first medium and arranging the subject in the second medium Calculating a second phase difference amount that is a difference between the measured first phase difference and the second phase difference and calculating a difference between the first wave front aberration and the second wave front aberration measured by disposing the subject in the first medium Calculating a first wave front aberration difference amount and calculating a second wave front aberration difference amount which is a difference between the first wave front aberration and the second wave front aberration measured by disposing the subject in the second medium, The refractive index distribution of the inspected object is removed by removing the shape components of the inspected object based on the retardation difference amount, the second retardation difference amount, the first wave front aberration difference amount, and the second wave front aberration difference amount Further comprising shipment.
3. The method according to claim 1 or 2,
Wherein the calculating step further comprises calculating a refractive index distribution of the inspected object based on the known shape of the object, the retardation difference amount, and the wave front aberration difference amount.
3. The method according to claim 1 or 2,
Measuring a wavelength dependency of a phase difference between the reference light and the light to be detected by disposing a medium having a group refractive index equal to a refractive index of the group of the object at a specific wavelength on the reference light and the light path of the light to be detected, Further comprising calculating the first wavelength and the second wavelength such that the first phase difference and the second phase difference become equal to each other based on the wavelength dependence of the first wavelength and the second wavelength.
3. The method according to claim 1 or 2,
A second reference lens whose shape and refractive index are known, and a second reference lens whose shape and refractive index are known, and the object to be examined is inserted between the first reference lens and the second reference lens, Further,
The phase difference measurement step may further include measuring a first phase difference at the first wavelength and a second phase difference at the second wavelength by interfering the reference light and the light having passed through the test unit with each other ,
The wavefront aberration measuring step may further include measuring a first wavefront aberration at the first wavelength and a second wavefront aberration at the second wavelength of the light having passed through the test unit,
Wherein the calculating step calculates a phase difference difference amount that is a difference between the first phase difference and the second phase difference and calculates a wave front aberration difference amount which is a difference between the first wave front aberration and the second wave front aberration, Further comprising calculating a refractive index distribution of the inspected object based on the shape and refractive index of the lens, the shape and refractive index of the second reference lens, the retardation difference amount, and the wave front aberration difference amount.
The method according to claim 6,
Wherein the phase difference measuring step includes the steps of disposing a first medium having a first refractive index between the first and second reference lenses and the inspected object to detect a first phase difference in the first wavelength and a second phase difference in the second wavelength, And a second medium having a second refractive index different from the first refractive index is disposed between the first and second reference lenses and the inspected object so that the first phase difference in the first wavelength and the second phase difference in the second wavelength are different from each other, Further comprising measuring a second phase difference at a second wavelength,
The wavefront aberration measuring step may include a step of arranging the first medium between the first and second reference lenses and the inspected object to detect a first wavefront aberration at the first wavelength and a second wavefront aberration at the second wavelength, Measuring aberration, arranging the second medium between the first and second reference lenses and the inspected object, and measuring a first wave front aberration at the first wavelength and a second wave front aberration at the second wavelength, Further comprising measuring,
Wherein the calculating step calculates a first phase difference amount that is a difference between the first phase difference and the second phase difference measured by disposing the first medium between the first and second reference lenses and the inspected object, Calculating a second phase difference amount that is a difference between the first phase difference and the second phase difference measured by disposing the second medium between the first and second reference lenses and the inspected object, Calculating a first wave front aberration difference amount which is a difference between the first wave front aberration and the second wave front aberration measured by disposing the first medium between the lens and the inspected object, A second wavefront aberration difference amount that is a difference between the first wavefront aberration and the second wavefront aberration measured by disposing the second medium between the object to be inspected is calculated, and the first phase difference amount, the second phase difference amount , The first wavefront number Further comprising calculating a refractive index distribution of the inspected object by removing the shape components of the inspected object on the basis of the second wave front difference amount and the second wave front aberration difference amount.
Molding the optical element,
A method of manufacturing an optical element comprising the step of evaluating optical performance of a molded optical element by measuring a refractive index distribution of the optical element using the refractive index distribution measuring method according to claim 1 or 2.
A light source,
A phase difference measurement unit for measuring a phase difference between the reference light and the light to be measured by dividing the light emitted from the light source into reference light and subject light and interfering with the reference light and the light to be examined, Sudan,
A wavefront aberration measuring means for measuring a wavefront aberration of the light to be detected,
And a calculating means for calculating a refractive index distribution of the inspected object based on the phase difference and the wavefront aberration, the refractive index distribution measuring apparatus comprising:
Wherein the phase difference measuring means measures a first phase difference at a first wavelength and a second phase difference at a second wavelength different from the first wavelength,
The wavefront aberration measuring unit measures a first wave front aberration at the first wavelength and a second wave front aberration at the second wavelength,
Wherein the calculating means calculates a phase difference difference amount that is a difference between the first phase difference and the second phase difference and calculates a wave front aberration difference amount which is a difference between the first wave front aberration and the second wave front aberration, And the wavefront aberration difference amount to calculate the refractive index distribution of the object to be examined.
10. The method of claim 9,
Wherein the wavefront aberration measuring means measures the transmitted wavefront of the inspected object at the first wavelength and the transmitted wavefront at the first wavelength of the reference inspected object having a specific refractive index profile, A first wavefront aberration is calculated as a difference between a transmission wavefront of the object to be inspected and a transmission wavefront of the reference inspected object at the first wavelength and a transmission wavefront of the object to be inspected at the second wavelength and a transmission wavefront of the object to be inspected at the second wavelength Wherein the second wavefront aberration is calculated as a difference between a transmission wavefront of the inspected object at the second wavelength and a transmission wavefront of the reference inspected object at the second wavelength by measuring a transmission wavefront of the reference inspected at the second wavelength, Distribution measuring device.
11. The method according to claim 9 or 10,
Wherein the retardation measurement means measures the first retardation at the first wavelength and the second retardation at the second wavelength by disposing the analyte in a first medium having a first refractive index, The second phase difference in the first wavelength and the second phase difference in the second wavelength are measured by arranging the analyte in a second medium having a second refractive index different from the first phase difference,
Wherein the wavefront aberration measuring unit measures the first wavefront aberration at the first wavelength and the second wavefront aberration at the second wavelength by disposing the object to be examined in the first medium, Measuring the first wave front aberration at the first wavelength and the second wave front aberration at the second wavelength by disposing the object to be examined,
Wherein the calculating means calculates a first phase difference amount that is a difference between the first phase difference and the second phase difference measured by disposing the subject in the first medium and arranges the subject in the second medium Calculating a second phase difference amount that is a difference between the measured first phase difference and the second phase difference and calculating a difference between the first wave front aberration and the second wave front aberration measured by disposing the subject in the first medium Calculating a first wave front aberration difference amount and calculating a second wave front aberration difference amount which is a difference between the first wave front aberration and the second wave front aberration measured by disposing the subject in the second medium, The refractive index distribution of the inspected object is removed by removing the shape components of the inspected object based on the retardation difference amount, the second retardation difference amount, the first wave front aberration difference amount, and the second wave front aberration difference amount Shipment, refractive index distribution measuring device.
11. The method according to claim 9 or 10,
Wherein the calculating means calculates the refractive index distribution of the inspected object based on the known shape of the object, the retardation difference amount, and the wave front aberration difference amount.
11. The method according to claim 9 or 10,
Measuring a wavelength dependency of a phase difference between the reference light and the light to be detected by disposing a medium having a group refractive index equal to a refractive index of the group of the object at a specific wavelength on the reference light and the light path of the light to be detected, And means for calculating the first wavelength and the second wavelength so that the first phase difference and the second phase difference become equal to each other based on the wavelength dependency of the first wavelength and the second wavelength.
11. The method according to claim 9 or 10,
And a second reference lens whose shape and refractive index are known, further comprising an inspection unit arranged to insert the inspection object between the first reference lens and the second reference lens and,
Wherein the phase difference measuring means measures the first phase difference at the first wavelength and the second phase difference at the second wavelength by interfering the reference light and the test light transmitted through the test unit,
The wavefront aberration measuring unit measures a first wavefront aberration at the first wavelength and a second wavefront aberration at the second wavelength of the light having passed through the test unit,
Wherein the calculating means calculates a phase difference difference amount which is a difference between the first phase difference and the second phase difference and calculates a wave front aberration difference amount which is a difference between the first wave front aberration and the second wave front aberration, Wherein the refractive index distribution of the object to be examined is calculated based on the shape and refractive index of the lens, the shape and refractive index of the second reference lens, the retardation difference amount, and the wave front aberration difference amount.
15. The method of claim 14,
Wherein the phase difference measuring means is arranged to position a first medium having a first refractive index between the first and second reference lenses and the inspected object to detect a first phase difference at the first wavelength and a second phase difference at the second wavelength, And a second medium having a second refractive index different from the first refractive index is disposed between the first and second reference lenses and the inspected object so that the first phase difference in the first wavelength and the second phase difference in the second wavelength are different from each other, The second phase difference at two wavelengths is measured,
The wavefront aberration measuring unit may be configured to position the first medium between the first and second reference lenses and the inspected object to detect a first wavefront aberration at the first wavelength and a second wavefront aberration at the second wavelength, Measuring aberration, arranging the second medium between the first and second reference lenses and the inspected object, and measuring a first wave front aberration at the first wavelength and a second wave front aberration at the second wavelength, And,
Wherein the calculating means calculates a first phase difference amount that is a difference between the first phase difference and the second phase difference measured by disposing the first medium between the first and second reference lenses and the inspected object, Calculating a second phase difference amount that is a difference between the first phase difference and the second phase difference measured by disposing the second medium between the first and second reference lenses and the inspected object, Calculating a first wave front aberration difference amount which is a difference between the first wave front aberration and the second wave front aberration measured by disposing the first medium between the lens and the inspected object, Calculating a second wave front aberration difference amount that is a difference between the first wave front aberration and the second wave front aberration measured by disposing the second medium between the object to be inspected and calculating a difference between the first retardation difference amount and the second retardation difference amount , The first wavefront number The second wave front aberration difference amount, and the second wave front aberration difference amount to remove the shape component of the object to be inspected, thereby calculating the refractive index distribution of the object to be inspected.
A light source,
A phase difference measurement unit for measuring a phase difference between the reference light and the light to be measured by dividing the light emitted from the light source into reference light and subject light and interfering with the reference light and the light to be examined, Sudan,
A wavefront aberration measuring means for measuring a wavefront aberration of the light to be detected,
And calculation means for calculating a refractive index distribution of the object to be examined based on the phase difference and the wavefront aberration, the refractive index measurement apparatus comprising:
Wherein the phase difference measuring means measures a first phase difference at a first wavelength and a second phase difference at a second wavelength different from the first wavelength,
The wavefront aberration measuring unit measures a first wave front aberration at the first wavelength and a second wave front aberration at the second wavelength,
Wherein the calculating means calculates a phase difference difference amount that is a difference between the first phase difference and the second phase difference and calculates a wave front aberration difference amount which is a difference between the first wave front aberration and the second wave front aberration, And calculates the refractive index distribution of the inspected object on the basis of the wavefront aberration difference amount and the refractive index distribution of the inspected object and the phase refractive index of the inspected object at the first wavelength on the basis of the first wave front aberration, .
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